Patellar malalignment is known as a translational or rotational deviation of the patella in any axis that causes aberrant dispersion of the forces transmitted through the patellofemoral joint. Ideally the patella is located centrally in the trochlear groove where the imposed forces of the quadriceps and the patella tendon are properly established over the patellofemoral joint. Malalignment of the patella, laterally, medially, rotationally, vertically or any combination thereof including tilt, can adversely impact the mechanics of the patellofemoral joint and cause pain during flexion of the knee. Observation of malalignment shows lateral misalignment to be more common than medial.
It has been known to apply positioning forces to the patella to resist mispositioning, such positioning forces being applied by many different types of devices.
A common positioning technique is the use of tape applied to the skin at the patella and tensioned in a direction chosen to accommodate proper positioning of the patella. One known example is the McConnel taping technique. While such taping for patellar subluxation may reduce abnormal movement of the patella and may assist in proper positioning, proper positioning of the tape and the proper application of force vectors generated by the taping are difficult to predictably, repetitively achieve. Additionally the tape itself is discomforting, temporary and may be unduly binding of the knee joint while placing undesirable tension on the skin.
As an alternative to taping it has been known to employ various types of knee braces and supports, including sleeves received about the leg and positioned over the knee. Such sleeves can include anterior patellar openings and may include affixed pads for restricting movement of the patella. One such sleeve device is shown, for example in U.S. Pat. No. 4,084,584. In such a construction, the fixed position of the pad with respect to the sleeve requires that all adjustment of the pad for effect on the patella be through adjustment of the position of the sleeve on the leg with the action of the pad being essentially static. Attempts to apply a dynamic force may be defeated by movement of the sleeve during normal or energetic flexion of the knee joint.
It has been suggested to apply adjustable biasing means either to patella-engaging pads fixed to the sleeve adjacent the anterior opening, such as shown in U.S. Pat. No. 4,296,774 or pads which are affixed to a separate tensioning body which may be received around the sleeve, such as shown in U.S. Pat. No. 5,613,943. While such devices provide some control over the degree of force exerted by the pad on the patella, that force is generally limited to a medial force such that the ability of the bracing pad to properly align the patella is limited.
It would therefore be an advance in the art to provide a patellar alignment system or brace having a wide range of adjustability which is comfortable to wear and which can apply forces to both the lateral and superior borders of the patella. It would be a further improvement in the art to provide such a brace that is self-conforming to the patella and where the force is applied over a wider area of contact with the patella in a direction offsetting the particular misalignment experienced by the patient.